Cava module regression after PR #4682: 'Unknown module' when no cava_config specified

[xav-ie]

After PR #4682 (merged Dec 18, 2025), the cava module fails with:

[warning] module cava: Disabling module "cava", Unknown module

This happens when using waybar's cava module without a cava_config file specified, which worked correctly before PR #4682.

Root Cause

The refactoring in PR #4682 introduced a mismatch between cava_backend.cpp and cava_frontend.hpp:

cava_backend.cpp

The output method is saved, temporarily set to RAW for initialization, then restored to the original value:

Save original output method:

Waybar/src/modules/cava/cava_backend.cpp

Line 184 in 97eb606

auto const output{prm_.output};

Restore original output method (BUG):

Waybar/src/modules/cava/cava_backend.cpp

Line 267 in 97eb606

prm_.output = output;

cava_frontend.hpp

The frontend only accepts OUTPUT_RAW or OUTPUT_SDL_GLSL, rejecting all other output methods:

Switch statement that throws "Unknown module":

Waybar/include/modules/cava/cava_frontend.hpp

Lines 14 to 25 in 97eb606

	const std::shared_ptr<CavaBackend> backend_{waybar::modules::cava::CavaBackend::inst(config)};
	switch (backend_->getPrm()->output) {
	case ::cava::output_method::OUTPUT_RAW:
	return new waybar::modules::cava::Cava(id, config);
	break;
	#ifdef HAVE_LIBCAVAGLSL
	case ::cava::output_method::OUTPUT_SDL_GLSL:
	return new waybar::modules::cava::CavaGLSL(id, config);
	break;
	#endif
	default:
	break;

Cava library default

When no config file is provided, cava defaults to OUTPUT_NONCURSES:

Default output method is "noncurses":
https://github.com/LukashonakV/cava/blob/256cf7aa7c893fb457d54477bd20758db3d79026/config.c#L819

Old code (pre-PR #4682)

The old implementation simply set OUTPUT_RAW once and never changed it:

Old cava.cpp:

Waybar/src/modules/cava.cpp

Line 22 in cbab9c9

prm_.output = cava::output_method::OUTPUT_RAW;

Flow Analysis

1. Waybar config has no cava_config option → empty path passed to load_config()
2. Cava library uses default output:method = noncurses → OUTPUT_NONCURSES
3. cava_backend.cpp saves OUTPUT_NONCURSES, sets to OUTPUT_RAW for init, then restores to OUTPUT_NONCURSES
4. cava_frontend.hpp calls getPrm()->output → gets OUTPUT_NONCURSES
5. Switch statement doesn't match OUTPUT_RAW or OUTPUT_SDL_GLSL
6. Falls through to throw std::runtime_error("Unknown module")

Steps to Reproduce

1. Use waybar built from current master (commit 97eb606 or later)
2. Add cava module to waybar config without cava_config option:

"cava": {
  "framerate": 60,
  "bars": 12,
  "method": "pulse",
  "format-icons": ["▁", "▂", "▃", "▄", "▅", "▆", "▇", "█"]
}

3. Run waybar
4. See warning: module cava: Disabling module "cava", Unknown module

Expected Behavior

Cava module should work without requiring a separate cava config file, as it did before PR #4682.

Suggested Fix

Either:

Option A: Don't restore the output method in cava_backend.cpp (line 267):

// prm_.output = output;  // Keep OUTPUT_RAW for waybar

Option B: Handle all output methods in cava_frontend.hpp, defaulting to raw Cava for non-GLSL methods:

switch (backend_->getPrm()->output) {
  case OUTPUT_SDL_GLSL:
    return new CavaGLSL(id, config);
  default:  // All other methods use raw text cava
    return new Cava(id, config);
}

System Info

• waybar version: 0.14.0+date=2025-12-18_97eb606
• OS: NixOS (Linux 6.18.2)
• Built with cava support from flake input github:Alexays/waybar

Workaround

Create a cava config file with explicit method = raw in [output] section and reference via cava_config in waybar config. But this shouldn't be necessary for basic usage.

[xav-ie]

I made a pr to fix this:
#4728

[xav-ie]

Hooray! the pr is merged :)